Limenitis rileyi. Picture courtesy: British Natural History Museum, London
Guwahati, Jan. 31: A butterfly, spotted in Arunachal Pradesh nearly three decades back, has been finally described as a new species.
The Limenitis rileyi Tytler was sighted by London-based naturalist Purnendu Roy in Upper Dibang Valley district in 1987, and has now been reported in the current issue of Journal of Threatened Taxa. "This sighting of L. rileyi represents the first record of this species from India, thus adding to India's butterfly fauna," the article says.
The species was previously recorded in southeast Tibet, Myanmar and northern Vietnam.
Roy had found a single male specimen on July 19, 1987, at a height of around 1,800 metres near Anini in Upper Dibang Valley in a wet sub-tropical broad-leaf forest.
A neighbouring subspecies, L. rileyi xizangana Huang, was recorded in southeast Tibet in 1998. The Dibang Valley record lies between southeast Tibet and northeast Myanmar records and fills a gap in the distribution. No subspecies determination has been made because of the sample size of one. Records of L. rileyi from southeast Tibet and northeast Myanmar indicate a flight period of June to August at altitudes between 1,600m and 2,400m.
"When I collected the butterfly back in 1987 in Upper Dibang Valley, there was no freely available literature to identify this species. Even now it is not illustrated on the Internet to my knowledge. H.C. Tytler unfortunately did not illustrate the species when he described it in 1940 from northeast Myanmar. At the time it was bit of a dead end for investigation so I had left it tentatively identified to a related species L. mimica that occurs in Myanmar and China.
"In 2012, my partner Jo persuaded me that I should spend more time on butterflies again. After hearing about the work of Sanjay Sondhi of Titli Trust, I contacted him and offered to assist in the surveying of moths and butterflies at Pakke tiger reserve and Eaglenest wildlife sanctuary. It was after that trip that I decided to approach the British Natural History Museum, London, to assist in identifying what I could not identify in 1987. David Lees identified the species as L. rileyi. He also recognised that another specimen I had was not described before, which I named Callerebia dibangensis in 2003," Roy told The Telegraph.
He said the butterfly is found in wet sub-tropical Montane forests at around 1,800m. Such areas can be inaccessible in monsoon owing to landslides and with frequent rains it can be a lottery to observe butterflies. Consequently, species that fly in monsoon like this species, maybe overlooked, he added.
Roy said habitat loss is the greatest risk to any species. Where the species was collected, the forest is quite fragmented and so locally could be at risk. There are larger forests where it may be less at risk but these are quite inaccessible or in protected areas. "I think it is essential that local biodiversity is conserved and that we are not just left with islands of biodiversity, inaccessible to most people and more vulnerable. For the lower forests, the proposed Dibang Valley dam is a major threat. Despite being initially rejected by the forest advisory committee in 2013, it has been given the go ahead again and some of India's finest forests will be destroyed," he said.
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